Machine Design

Hummer Humdinger

The AM General Hummer was in its element during rain-soaked runs at the Dana proving grounds.

Visible on the Hummer chassis, a full ladder box frame, is the transfer case that helps give the vehicle its true four-wheel drive.

A cutaway view of a Hummer geared hub reveals the half axle and spindle. The spindle is drilled through its center to accommodate air on-the-move tire deflation/inflation. Air is from an onboard compressor.

Suspension components on the left front wheel illustrate where the Hummer gets its large 3.5-in. jounce, 4.5-in. rebound wheel travel.

AM General Corp.'s Rick Fanco started to chuckle when he first heard some of the laudatory comments Best Ride judges made about the Hummer. "It does handle a lot better than what most people expect," he says. "The Hummer might be a little firm on the highway but it rides like a Cadillac off road." Fanco, manager of chassis engineering for the Hummer and Humvee, has been involved with the vehicle nearly since its inception in the late 1970s.

"The original spec called for a stable, mobile platform with high ground clearance," he says. "We designed the ride and handling to mainly minimize shock to the driver and cargo. Use of a fully independent suspension gives the vehicle a good ride and lets it keep as many wheels on the ground as possible." Today's civilian Hummer is nearly identical to the Humvee designed to military specs. The only differences in the chassis and power train are the 10.5-in. brake drums and ABS on the civilian Hummer (The military Humvee carries 12-in. rotors. ABS is scheduled for the future.) and a 6.5-liter turbo-diesel V8. Interestingly enough, diesels on all but the heavy-duty military Humvees are naturally aspirated. "The extra 35 hp and 150 lb-ft of torque from the turbo makes the vehicle so much more responsive that we decided it should be standard equipment on the civilian version," says Fanco.

The Hummer's 16-in. ground clearance (double that of most 4 4s) comes courtesy of torque-doubling geared hubs on all four wheels. Power reaches the ground through a 1.92:1 gear-reduction box at each wheel that also allows the axle half shafts to be 3.5 in. higher than the wheel spindle. Shock-in-coil spring suspension elements at all four corners and a front stabilizer bar round out the suspension design. Rear coil springs are tapered to provide a variable rate and stiffen up under heavier loads.

Big 16.5-in. steel and 17-in. aluminum rims hold tires specially designed for the Hummer, helping to give the vehicle stability. This, coupled with a CG of only 32 in. at curb weight, lets the Hummer climb 60° grades and travel on 40° side slopes. Probably much to the relief of most judges, neither of these impediments were part of the Best Ride course. Good thing: No other vehicle in the field could have handled such obstacles.

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